With the advancement of information communication technologies, various wireless communication technologies have recently been developed. Among the wireless communication technologies, a wireless local area network (WLAN) is a technology whereby Internet access is possible in a wireless fashion in homes or businesses or in a region providing a specific service by using a portable terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), etc.
The IEEE 802.11n is a technical standard relatively recently introduced to overcome a limited data rate which has been considered as a drawback in the WLAN. The IEEE 802.11n is devised to increase network speed and reliability and to extend an operational distance of a wireless network. More specifically, the IEEE 802.11n supports a high throughput (HT), i.e., a data processing rate of up to above 540 Mbps, and is based on a multiple input and multiple output (MIMO) technique which uses multiple antennas in both a transmitter and a receiver to minimize a transmission error and to optimize a data rate.
With the widespread use of the WLAN and the diversification of applications using the WLAN, there is a recent demand for a new WLAN system to support a higher throughput than a data processing rate supported by the IEEE 802.11n. A next-generation WLAN system supporting a very high throughput (VHT) is a next version of the IEEE 802.11n WLAN system, and is one of IEEE 802.11 WLAN systems which have recently been proposed to support a data processing rate of above 1 Gbps in a MAC service access point (SAP).
The plurality of STAs, MU-MIMO paired with the AP, may have different capabilities. In this case, a supportable bandwidth, modulation coding scheme (MCS), forward error correction (FEC), etc., may vary depending on an STA type, usage, channel environment, etc.
In a WLAN system supporting MU-MIMO transmission, transmission target STAs are grouped into a group for MU-MIMO transmission. The transmission target STA group can be identified by a group ID. Meanwhile, since one STA can be included in at least one transmission target STA group, at least one group ID can be allocated.
Meanwhile, as the WLAN system applies to a broader area and a wireless apparatus supporting the WLAN is distributed actively, there may be a problem in that a group ID is overlappingly allocated to STAs. In MU-MIMO transmission, the group ID corresponds to information identifying which STA is a transmission target STA, and thus the overlappingly allocated group ID may be a factor that obstructs MU-MIMO transmission. Therefore, a method supporting packet transmission and reception for MU is required in a WLAN system in which there is a possibility that a group ID is overlappingly allocated.